This invention relates to zoom viewfinders.
Reverse Galilean-type viewfinders which include a projected frame or reticle easily delineate the field of view. When we eliminate the reticle or the frame, controlling the field of view becomes more difficult. Merely changing magnification does not guarantee that as we zoom we will see the correct field of view (FOV), because the aperture (window) that limits the FOV may appear to change size resulting in a variation in the apparent FOV. Finally, if the optical system in a viewfinder has system distortion and pupil distortion, the field of view will not be properly delineated. An optical designer often attempts to eliminate the system distortion, but that comes at the expense of not minimizing other aberrations. In addition, pupil distortion may cause the clipping of the edges in the field of view if the aperture of the field stop (i.e. framing window) is of the conventional rectangular shape.